Metal refining



April 121i 1932- J. o. BETTERTON 1,853,535

METAL REFINING Original Filed Oct. 5l. 1929 silver and bismuth are removed by suitable' Patented Apr. l12, A193:2 v

Y UNITED" STATES APa'rlszN'r ori-ICE JESSE OATMAN BETTERTON, OE OMAHA, NEBRASKA, ASSIGNOB T0 AMERICAN SMELT- ING AND BEFINING COMPANY, OF NEW YORK, N. Y., -A CORPORATION 0F NEW JERSEY METAL BEFININ G Application led Octoberl, 1 929, Serial No. 403,920. Renewed September 2, 1931. p

added and blocks are formed as the bath is This invention relates to the refining of metals, and more particularly to the removal of silver and bismuth from lead.

In accordance with the present invention,

reagents such as zinc and calcium respectively incontinuous operation without intermediate cooling of the bath. After the metal has been suitably treated by the above reagents,. the excess of said reagents is removed simultaneously by the addition of suitable amounts of chlorine which combines with the zinc and calcium to form chlorides of these elements. The invention also provides for the selective -recovery of the above elements and the selective recovery Aof the excess reagents whereby the cost of operation is reduced to a The invention further consists-in the new and novel features of operation and the new and original arrangements and combinations of steps in the process hereinafter-described and more particularly set forth in the claims. Although the novel features which are be lieved to be characteristic of this invention will be particularly pointed out in the claims appended hereto, the invention itself, as to its objects and advantages, the mode of its operation and the manner of its organization maybe better understood by referring to the following description in which a particular commercial embodiment thereof is disclosed. It will be understood, however, that the processes and the steps thereof may be modiied in various respects without departing from the broad spirit and scope of the invention. Y A Y n In the following description and in the claims the various steps in the process and the details comprising the invention will be identified by specific names for convenience but they are intendedto -be as generic in their application as the art will permit.

' The present process is carried out by heating the bath of lead to a suitable ltemperature; after which a quantity of zinc is added suiiicientto form a silverdross which may be removed and treated for the recovery of silver therefrom. -After the major portion of the silver has been removed zinc plates are gradually cooled. Theseiblocks contain the further quantities 'of silver and are used as a is reheated and chlorineA is applied which .combines with the`zinc and calcium to roduce chlorides of these elements in 'ch form they are removed from the bath. The silver and bismuth content of the bath is thus reduced to the required percentage and the metal is in condition for use in further relining which may be carried out in a manner well known in the art: Y

The drawing forming a part of this application vshows a' flow sheet illustrating the process. v g

As a specific example of a manner in which this process ma be carried out, a bath of lead bullion is eated to a temperature of 875 to 900 F., after which zinc and blocks from previous refining operations are added while suitable stirring the bath to produce the desired reaction. A zinc-silver dross is formed which is skimmed and may be pressed to largely remove the lead therefrom. The

dross "is then sent to the retorts wherein the silver may be recovered in the usual manner.

After the dross is removed the bath is allowed to gradually cool while-zinc plates are added. Further quantities of dross are then the bath had reached a temperatureof 650 lo three blocks were formed in the manner pointed out above together with rims as thepmctal adjacent the sides of the Container solidified. These blocks and rims were removed and used for treatment of subsequent baths. The bath was then reheated and chlorine was added in suiicient quantity to unite with the calcium and zinc to form slags of zinc chloride and calcium chloride. The first slags contained all of the calcium as calcium chloride with some of the zinc as zinc chloride,

4and may `be used for treating high bismuth drosses. The final slags are free from calcium chloride and represent the normal zinc 'chloride salt, which may be used in any Well known manner. The first slag may be used for the treatment of the bismuth containing dross for the removal of the calcium and its separation from the zinc and bismuth contained in the dross. i

A suitable means of treatin the dross which, however, forms no part o the present invention but is covered in my vco-penditgV application Serial No. 424,134, filed January 28, 1930, for metal refining, comprises vmelting the same under a zinc chloride, calcium chloride slag at a temperature of approximately 1000c F. and skimming the resulting slag which will contain the zinc chloride, calcium chloride andany calcium which may have been contained inthe dross. The resulting bath is free from calcium and may be treated by liquation for the removal of the zinc. These liquations are retorted and metallic zinc to the extent of 3.6 lb. per t. original bullion recovered and again used in the desilverizing. The residual metal after rctorting the zinc liquations is combined with the bath from which these zinc liquations were removed, and the combined bath treated with chlorine gas for the removing of any remaining zinc. The zinc chlorideslag is combined with the zine chloride, calcium chloride slag mentioned 'above andthe bath may be treated as desired for the recovery of bismuth.

In the above process. the bismuth-calciumzinc dross 4contains approximately 5%' by weight of the bullion treated and is so processed as to allow the recovery of the zinc as metallic zinc whichis in suitable condition for further use in desilverization. The quantity'v of zinc chloride slag which is produced kin exccssofvthat which can be used for the above described process is reduced to a .minimum and the operating time is materially decreased. In a certain instance the operating time for the debismuthing prooem amounted to approximately 4 hours which was divided as follows: Charging alloy, 20 minutes; melting alloy, 2O minutes; stirring alloy, 30 minutes; skimming bismuth dross,

2 hours, 50 minutes.

Although certain novel features .of the invention have been shown and described and are pointed out-in the annexed claims, it will be-understood that various omissions, substi` tutions andchanges in the forms and details of the devices illustrated and in its operation may be made by those skilled in the art without departing from the spirit of the invention.

What is claimed is:

1. The process of treating lead which comprises heating a bath of said lead, adding zinc to said bath whereby a zinc-silver `dross is produced, skimming said dross, adding a calcium-lead .alloy thereto whereby a bismuth-calcium-lead dross is produced, removing said dross and treating the bath with chlorine for the removalof calcium and zinc therefrom.

`2. The treatment of lead bullion for the removal ofsilver and bismuth which comprises removing the silver as a. zinc silver dross and removing the bismuth as a calciumbismuth dross and subsequently removing the zinc and calcium by means of chlorine.

3. rl`he process of treating lead bullion for the removal of silver and bismuth which comprises heating said bullion, adding zinc thereto and stirring to produce a zinc-silver dross, removing said dross, adding calciumlead alloyv and stirring to produce a calcium-v lead-bismuth dross, removing said dross, addv ing further quantities of zinc and forming blocks and rims as the bath is further cooled,

and adding chlorine gas to the bath to form a i slag of calcium chloride and zinc chloride.

Ll. The process of treating lead bullion for the removal of silver and bismuth which comprises heating said bullion, adding zinc thereto and stirring to produce a zinc-silver dross, removing said dross, adding calcium-lead alloy to produce a calcium-lead-bismuth dross,

removing said dross, adding chlorine gasto form a slag of calcium chloride and zinc chloride, removing a first slag containing substantially the entire calcium content and re'- moving a second slag which comprises essentially zinc chloride.

5.' The process of treating lead bullion for the removal of silver and bismuth which comprises heating said bullion, adding zinc thereto and stirring to produce a zinc-silver dross, removing said dross, adding further quantities of zinc while the metal is slowly cooled, removing further quantities of dross, adding calcium-lead alloy and stirring t0 produce a calcium-lead-bismuth dross, removing said dross, and adding chlorine gas to form a slag of calcium chloride and zinc chloride.

6. The process of treating lead bullion for the removal of silver and bismuth which comprises heating said bullion, adding zinc therel the removal of silverand bismuth which comprises heating said bullion to a temperature of 87 0 F., adding zinc thereto and stirring to produce a zinc-silver dross, removing said dross, allowingthe bath to cool to a temperature of approximately 650 F., add-` ing calcium-lead alloy and stirring ,to produce a calcium-lead-bismuth dross, removing said dross, and adding chlorine gas to form a slag of calcium chloride and zinc chloride. 8. The process of treatin lead bullion for the removal of silver an bismuth which comprises heating said bullion to a temperature of 870 F., adding zinc thereto and stirring to produce a zinc-silver dross, removing said dross, addin further quantities of zinc while the metal 1s slowly cooled, removing further quantities of dross, allowing the bath to cool to a temperature of approximately 650 F., adding calcium-lead alloy and stirring to produce a calcium-lead bismuth dross, removing said dross, adding further quantities of zinc and Jforming blocks and rims as the bath is further cooled, reheatin 'the bath to a proper molten state, adding ch orine gas to form a slag of calcium chloride and zinc chloride, removing a `first slag containing substantially the entire calcium content and removing a Asecond slag which comprises essentially zinc chloride.

9. In the process of desilverizing lead by' the addition of zinc as a reagent and debismuthizing lead by the addition of a reagent capable of forming al bismuth-containing dross, the improved steps which comprise adding the debismuthizing reagent to 'the lead in the presence of the residual zinc remaining from desilverization and subsequently treating the bath to eit'ect the re'- moval of the zinc and the debismuthizing reagent as a dross.

10. The process of refining lead containing silver and bismuth Vwhich com rises melting said lead to form a molten bath, incorporating a zinc yielding substance in said molten bath to @Heet the removal of silver, subsequently adding calcium to said lead con-v taining residual zinc 'remaining from the desilverization of said lead to effect the removal of bismuth, and then introducing a reagent capable of removing calcium and zinc as a dross from' said bat 11. The process set forth in claim 10 inv which the bath is maintained in a molten condition throughout the desilverizing and debismuthizing operation.

In testimony whereof I have hereunto set my hand.

JESSE QATMAN BETTERTON. 

